GFR Calculator - Glomerular Filtration Rate Calculator & Kidney Function Calculator
Free GFR calculator to estimate your Glomerular Filtration Rate (GFR). The GFR (glomerular filtration rate) Calculator estimates GFR values based on factors including serum creatinine value, age, race, and gender. For comparison purposes, the results for three prevalent formulas used for estimating GFR are provided: MDRD Study Equation, CKD-EPI Formula, and Mayo Quadratic Formula. For children, the Schwartz formula is used.
Last updated: January 20, 2026
Need a custom medical calculator for your platform? Get a Quote
Must be 18 years or older
GFR Results
MDRD Study Equation
89 mL/min/1.73 m²
CKD-EPI Formula
99 mL/min/1.73 m²
Mayo Quadratic Formula
120 mL/min/1.73 m²
Average GFR
103 mL/min/1.73 m²
Estimated CKD Stage
Normal or CKD1
Important Notes:
- • GFR values are estimates and should be interpreted by a healthcare professional
- • Normal GFR: 100-130 mL/min/1.73 m² (men), 90-120 mL/min/1.73 m² (women under 40)
- • GFR decreases with age after 40
- • Multiple formulas provide different estimates; consult your doctor for interpretation
Understanding GFR
What is Glomerular Filtration Rate (GFR)?
Glomerular filtration rate describes the rate of flow of filtered fluids through the kidney and is used as a measure of kidney function. Generally, a higher value of GFR indicates better kidney function. A significant decrease in GFR indicates that the kidney is not properly functioning, resulting in lower volumes of fluids being filtered over a given time. The normal range of GFR adjusted for body surface area is 100 to 130 mL/min/1.73 m² in men and 90 to 120 mL/min/1.73 m² in women below the age of 40. After age 40, GFR decreases progressively with age.
Population Mean Estimated GFR
| Age | Mean Estimated GFR (mL/min/1.73 m²) |
|---|---|
| 20-29 | 116 |
| 30-39 | 107 |
| 40-49 | 99 |
| 50-59 | 93 |
| 60-69 | 85 |
| 70+ | 75 |
Chronic Kidney Disease Stages
A GFR above 60 mL/min/1.73 m² is usually adequate for most patients and alone is not necessarily indicative of a patient having chronic kidney disease (CKD). If, however, there has been a significant decline of GFR since a previous test, this could be an early indicator of kidney disease. Note that the sooner that kidney disease is diagnosed and treated, the higher the probability that the need for dialysis can be prevented. Below is a table of GFR ranges for the different stages of CKD. The different stages are dependent on other factors in conjunction with GFR, as noted in the table.
| Stage | GFR Value (mL/min/1.73 m²) |
|---|---|
| Normal | 90+ or above and no proteinuria |
| CKD1 | 90+ with evidence of kidney damage |
| CKD2 (Mild) | 60 to 89 with evidence of kidney damage |
| CKD3 (Moderate) | 30 to 59 |
| CKD4 (Severe) | 15 to 29 |
| CKD5 Kidney failure | less than 15 |
How Our GFR Calculator Works
Measuring GFR
The most accurate way to determine GFR involves the measurement of the rate at which an external substance such as inulin is removed from the bloodstream, termed inulin clearance. Inulin is freely filtered by the kidney and does not undergo metabolism, tubular secretion, or absorption, making it an ideal candidate for measuring GFR. This measurement method requires continuous intravenous infusion, a number of blood and urine collections, and proper timing of blood samples, making it impractical for routine clinical use.
As such, many formulas have been developed to estimate GFR, many of which are based on creatinine clearance, or estimates of creatinine clearance based on serum creatinine levels. Creatinine clearance does, however, have the limitation of being affected by muscle mass. Higher muscle mass increases serum creatinine for any given rate of clearance. This means that the same serum creatinine values can signify different levels of renal function for different people based on muscle mass. Furthermore, creatinine is actively secreted in small amounts in the body resulting in GFR determined through creatinine clearance typically being overestimated by 10-20%. Despite its limitations, creatinine clearance still provides an acceptable estimation of GFR due to its ease of measurement when compared to inulin clearance.
GFR Calculation Formulas
GFR = 175 × (SCr)-1.154 × (age)-0.203 × (0.742 if female) × (1.212 if Black)
where SCr = serum creatinine in mg/dL
Black female:
If SCr ≤ 0.7: GFR = 166 × (SCr/0.7)-0.329 × 0.993age
If SCr > 0.7: GFR = 166 × (SCr/0.7)-1.209 × 0.993age
Black male:
If SCr ≤ 0.9: GFR = 163 × (SCr/0.9)-0.411 × 0.993age
If SCr > 0.9: GFR = 163 × (SCr/0.9)-1.209 × 0.993age
Non-Black female:
If SCr ≤ 0.7: GFR = 144 × (SCr/0.7)-0.329 × 0.993age
If SCr > 0.7: GFR = 144 × (SCr/0.7)-1.209 × 0.993age
Non-Black male:
If SCr ≤ 0.9: GFR = 141 × (SCr/0.9)-0.411 × 0.993age
If SCr > 0.9: GFR = 141 × (SCr/0.9)-1.209 × 0.993age
If SCr < 0.8 mg/dL, use 0.8 mg/dL for SCr
GFR = e(1.911 + 5.249/SCr - 2.114/SCr2 - 0.00686 × age - (0.205 if female))
GFR = 0.413 × height(in cm) / SCr
Need help with other medical calculations? Check out our blood pressure calculator, liver function calculator, and other medical tools.
Get Custom Calculator for Your PlatformGFR Calculator Examples
Input Values:
- Serum Creatinine: 0.9 mg/dL
- Age: 50 years
- Gender: Male
- Race: Not Black
Results:
- MDRD: ~90 mL/min/1.73 m²
- CKD-EPI: ~95 mL/min/1.73 m²
- Mayo: ~88 mL/min/1.73 m²
- Average: ~91 mL/min/1.73 m²
- CKD Stage: Normal or CKD1
Interpretation: The GFR values indicate normal kidney function. All three formulas provide similar estimates, which is typical when kidney function is within normal range.
Frequently Asked Questions
Found This Calculator Helpful?
Share it with others who need help with GFR and kidney function calculations